Impact wrench with separate inertia means



Aug. 11, 1964 Filed May 19, 1961 H. C- REYNOLDS IMPACT WRENCH WITHSEFARATE INERTIA MEANS 2 Sheets-Sheet 1 HIS INVENTOR HAROLD O. REYNOLDSATTORNEY Aug. 11, 1964 H. c. REYNOLDS IMPACT WRENCH WITH SEPARATEINERTIA MEANS 2 Sheets-Sheet 2 Filed May 19, 1961 INVENTOR HAROLD c.REYNOLDS BY ATTORNEY United States Patent 3,144,108 IMPACT WRENCH WITHSEPARATE INERTIA MEANS Harold C. Reynolds, Athens, Pa., assignor tolngersoll- Rand Company, New York, N.Y., a corporation of New JerseyFiled May 19, 1961, Ser. No. 111,198 7 Claims. (Cl. 19230.5)

This invention relates to impact wrenches and particularly to that typeof impact wrench in which a hammer is adapted to strike a succession ofblows in a rotary direction upon a member carrying a suitable workengaging tool such as a screwdriver blade, wrench socket and the like.

The invention is particularly useful as applied to that type of wrenchin which the hammer member is directly connected to the driving motor sothat the mass of the motor and the hammer element combine to exert theirkinetic energy on the work. In this type of wrench it is customary toprovide jaws movable on the hammer for engagement with a part generallycalled the anvil. Such jaws are moved into engagement with the anvil bya cam and upon striking the blow means, somewhat in the nature of a camis provided for disengaging the jaw to permit rotation of the hammer toresume. An undesirable feature of constructions heretofore employed isthat the means for disengaging the dog from the anvil starts to act evenbefore the instant of impact thus resulting in a rubbing contact at theinstant maximum pressure exists between the two impacting partsproductive of a bad wearing condition therebetween.

By this invention means is provided to delay the disengagement of thedog from the anvil until after the impact and the motion of the hammerwith respect to the anvil has stopped. This means additionally has theeffect at the instant of contact of the dog with the anvil of holdingthe hammer dog in the striking position positively or if desired tocontinue the motion of the hammer dog into the clutching direction evenafter striking the hammer blow.

Thus the invention has for its object to produce an impact clutch for awrench or similar tool with an improved striking mechanism withrelatively little wear on the striking faces, economical to maintain andsimple to construct.

Other objects and advantages of the invention will be in part pointedout and in part obvious hereinafter.

A preferred embodiment of the invention is illustrated in the drawing inwhich FIGURE 1 is a longitudinal section of the front end of an impactwrench at the impacting mechanism,

FIG. 2 is a transverse section of the impact clutch taken along the line22 of FIG. 1 looking in the direction of the arrows,

FIG. 3 is a transverse section taken along the line 3-3 of FIG. 1looking in the direction of the arrows,

FIG. 4 is a transverse section similar to that of FIG. 2 showing thehammer dog in position released from the anvil,

FIG. 5 is a perspective view of the cage of the hammer mechanism,

FIG. 6 is a perspective view of a sleeve for enclosing the inertiamember of the hammer mechanism,

FIG. 7 is a perspective view of the inertia member of the hammermechanism, being broken away at one side to show the construction in theopposite wall,

FIG. 8 is a perspective view of an end plate of the hammer mechanism,

FIG. 9 is a perspective view of one of the hammer dogs,

3,144,1h3 Patented Aug. 11, 1964 FIG. 10 is a perspective view of theupper portion of the anvil, and

FIG. 11 is an enlarged fragmentary plan view of the upper portion of theanvil showing the position of the striking face of the anvil jaw withrespect to the longitudinal axis of the anvil.

Referring to the drawing, impact wrench 10, of which only the fore partis shown, composed of a motor casing 12 to which is attached a hammercasing 14 having nose portions 16 rotatably supporting an anvil member18 projecting therefrom for attachment with a suitable work engagingimplement such as the wrench socket 20. Pro jecting from motor casing 12is provided a motor shaft 22 fluted at its end 24 to engage acorresponding fluted aperture 26 of a hammer element in the form of acage 28 (FIG. 5) encircling the rear end of anvil 18.

Anvil 18 is adapted to rotate in a bearing sleeve 30 having a flangedend 36 upon which rests a bearing plate 40 shown in detail in FIG. 8 andhaving a central flange 42 fitting closely around the front bearing endof anvil 18 and abutting a collar portion 44 so that in position shownin FIG. 1 plate 40 lies between collar 44 and the flanged portion 36 ofbearing sleeve 30. Plate 410 forms an end bearing for hammer cage 28 sothat cage 28 is rotatable by motor shaft 22 one end bearing againstplate 40 and the other against a collar 46 of shaft 22. Anvil 18 isadapted to be periodically engaged by the hammer mechanism and for thispurpose is provided with a pair of jaws 48 in this instancediametrically opposed to each other and separated peripherally by spaces5%? of lesser diameter terminating at jaws 48 in striking surfaces 52.

For this engagement by the hammer mechanism there are provided dogs 54,two in number, carried by cage 28 on longitudinally disposed pins 56fitting in bores 58 provided at the bottom of cage 28 and bores 6% inlongitudinal alignment with bores 58 at the opposite end of cage 28.Pins 56 fit into longitudinal bores 62 formed in dogs 54 and form abearing to permit oscillation of dogs 54 with respect to cage 28 asindicated in FIG. 2 and FIG. 4. With respect to jaws 48, dogs 54 rocksomewhat as the escapement of a clock movement and to carry out theanalogy, dogs 54 are provided with striking faces 64 between which thedog contour is arcuate as indicated at 66. As best shown in FIG. 11, thejaws 48 of anvil 18 are constructed so that each striking face 52 liesin a plane A-A extending at a relatively small acute angle with respectto a radial plane B-B extending from the longitudinal axis C of anvil18, the planes intersecting at the outer periphery of jaws 48. Each ofthe striking faces 52 of the anvil lying in a plane as above set forthprovides a camming surface for the impinging faces 64 and 52 of dogs 54and anvil 18, respectively, which camming surface is not sufficient tocause disengagement of those faces, while an inertia member 68,hereinafter fully described, rotates but is effective upon non-rotationof the inertia member to cause disengagement of the impinging faces aswill be more fully described hereinafter. As indicated in FIG. 2 whenthe forward striking face 64 hits, striking the corresponding strikingface 52 of anvil 18, the tendency is to glance off which will move thetail end striking face 64 inwardly as shown in FIG. 4. Then as dog 54moves around anvil 18 the tail end of the dog engages the correspondingjaw 48 to rock dog 54 again into the striking position of face 64 withrespect to the next face 52 of the anvil. The glancing off betweenstriking face 64 and the anvil striking face 52 has the effect ofminimizing the effectiveness of the blow, and the reduction of theangularity of faces 64 with respect to the center of rotation on pin 56is not entirely the complete solution as it would appear to be in someconstructions heretofore used, as above referred to, inasmuch as in thatcase the camming effect of the striking faces is merely replaced by acam drive arrangement which provides lost motion between the driver andthe hammer dog and has the effect of softening the blow.

This invention provides a means to prolong the contact between strikingfaces 64 and 52. It ceases to act very shortly after the blow isdelivered. To this end the invention provides the inertia member 68 ofconsiderable mass which is in the form of a sleeve encircling cage 28and adapted to rotate thereon. Inertia member 68 is provided withnotches 79 which are arranged to engage projecting tail portions 72formed integrally with dogs 54 and which project beyond cage 28. Asleeve 74 encircles inertia member 63 and when in place as part of thehammer mechanism it is so held by contact with the plate 40 at thebottom and a flange 76 projecting from the upper portion of cage 28.Sleeve 74 has the effect of reinforcing inertia member 68 and in case ofbreakage would prevent escape of broken parts and general wreckage ofthe machine.

In operation, and assuming clockwise rotation of the cage by motor shaft22 (FIG. 2 and FIG. 4), and assuming that the parts start in theposition shown in FIG. 4 wherein the tail end of dog 54 lies in thespace 50 between striking faces 52, rotation of cage 28 with respect toanvil 18 brings the tail end of dog 54 into contact with the jaw 48 torock dog 54 which in turn accelerates the inertia member 68 through thetail portion 72. The camming effect of dogs 54 and jaws 4S rocks the dog54 so that the forward striking face 64 is moved inwardly into the space50 and although this may not cause the forward striking faces 64 tobottom on the surface 50, still, at the instant of contact betweenstriking face 64 and face 52 to stop rotation of cage 28, the inertia ofmember 68 will be suflicient to continue the rocking effect of dog 54and to oppose any outward glancing of face 64. In fact it will tend tomove dog 54 into deeper contact with face 52. However, after stopping ofinertia member 68, the glancing effect or camming whichever may seem themore appropriate term of face 64 with respect to face 52 can now takeplace to disenagage those faces as indicated in FIG. 4 whereupon thecycle of operation is repeated.

For the reception of socket 20 on the end of anvil 18, in this instance,the end as shown at 80 is squared and socket 20 is held in place by setscrew 82. To indicate a suitable type of work to be performed, socket 20is shown in engagement with the nut 84 of a bolt or stud 86 mounted in aplate 88.

It is understood that the motor for attachment to shaft 22 may be of anysuitable description, electric or pneumatic, as will be understood. Forthis purpose an electric motor is not preferred since the intermittentstopping is not beneficial. Also, shaft 22 is provided preferably withsuitable anti-friction bearings 90 mounted in motor casing 12 and theattachment of motor casing 12 to the hammer casing 14 may be by means ofstuds 92.

As a matter of preferred construction, cage 28 is shown with an embossedportion 94 projecting from the upper face to elongate the flutedaperture 26 for firm and rugged connection with the fluted end 24 ofguide shaft 22. It will also be noted that the bore 60 in the upper endof cage 28 passes into boss 94 and terminates in a smaller bore 96 whichprovides an abutment to limit endwise movement of pins 56.

Thus by the above construction are accomplished, among others, theobjects hereinbefore referred to.

I claim:

1. An impact wrench comprising:

(a) a casing,

(b) an impact hammer mechanism rotatably disposed within said casing,

(c) an anvil rotatably disposed Within said casing and Within saidimpact hammer mechanism,

(d) cam means disposed on said anvil and operatively associated withsaid impact hammer mechanism to positively move said hammer mechanism inclutching and declutching directions with said anvil, and

(e) separate inertia means disposed on said impact hammer mechanism todelay the motion of said impact hammer mechanism into said declutchingdirection.

2. An impact wrench comprising:

(a) a casing,

(b) a rotatable anvil disposed in said casing,

(c) an impact hammer mechanism disposed in said casing encircling saidrotatable anvil, said impact hammer mechanism being rotatable about anaxis parallel to said anvil,

(d) cam means disposed on said anvil and operatively associated withsaid impact hammer mechanism to positively move said impact hammermechanism in clutching and declutching directions with said anvil, and

(e) means disposed on said impact hammer mechanism to delay the motionof said impact hammer mechanism in said declutching direction includinga separate inertia member carried by said impact hammer mechanism.

3. An impact wrench comprising:

(a) a casing,

(b) a rotatable anvil disposed in said casing,

(c) a revoluble impact hammer mechanism disposed in said casingencircling said anvil,

(d) a dog disposed on said revoluble impact hammer mechanism pivotedabout an axis parallel to said anvil and movable into clutching anddeclutching directions with said anvil,

(e) cam means disposed on said anvil and operatively associated withsaid dog for positively moving said dog in said clutching anddeclutching directions, and

(1) separate inertia means disposed on said revoluble impact hammermechanism to delay the motion of the dog in the declutching direction.

4. An impact wrench comprising:

(a) a casing,

(b) a rotatable anvil disposed in said casing,

(c) a revoluble impact hammer mechanism disposed in said casingencircling said anvil,

(d) a dog disposed on said revoluble impact hammer mechanism pivotedabout an axis parallel to said anvil and movable into clutching anddeclutching directions with said anvil,

(e) cam means disposed on said anvil and operatively associated withsaid dog for positively moving said dog in said clutching anddeclutching directions, and

(f) means disposed on said revoluble impact hammer mechanism to delaythe motion of the dog in the declutching direction including a separateinertia member carried by said revoluble impact hammer mechanism.

5. An impact wrench comprising:

(a) a casing,

(b) a rotatable anvil disposed in said casing,

(c) a hammer mechanism disposed in said casing rotatable about an axisparallel to said anvil,

(d) a dog disposed on said hammer mechanism movable into clutching anddeclutching directions with said anvil,

(e) cam means disposed on said anvil and operatively associated withsaid dog for positively moving said dog in said clutching direction tostrike a blow,

(f) separate inertia means disposed in said hammer mechanism to continuethe motion of said dog in said clutching direction after striking saidblow, and

(g) means to move said dog in said declutching direction.

6. A11 impact wrench as set forth in claim 5 in which said separateinertia means to continue the motion of said hammer mechanism includesan inertia member acmated by said cam means.

7. An impact wrench as set forth in claim 6 in which said inertia memberis engaged by said dog and is accelerated thereby.

References Cited in the file of this patent UNITED STATES PATENTSRueckart et a]. Jan. 31, 1933 Moretti Dec. 26, 1939 Amtsberg June 9,1942 Jimerson Sept. 27, 1955 Schmid Aug. 13, 1957

1. AN IMPACT WRENCH COMPRISING: (A) A CASING, (B) AN IMPACT HAMMERMECHANISM ROTATABLY DISPOSED WITHIN SAID CASING, (C) AN ANVIL ROTATABLYDISPOSED WITHIN SAID CASING AND WITHIN SAID IMPACT HAMMER MECHANISM, (D)CAM MEANS DISPOSED ON SAID ANVIL AND OPERATIVELY ASSOCIATED WITH SAIDIMPACT HAMMER MECHANISM TO POSITIVELY MOVE SAID HAMMER MECHANISM INCLUTCHING AND DECLUTCHING DIRECTIONS WITH SAID ANVIL, AND